This simulation demonstrates the effect of the correlation between measures in a one-way within-subjects ANOVA with two levels. This test is equivalent to a correlated t test. The default values for this demonstration are for an experiment with 10 subjects each measured under two conditions. The population difference for the two conditions is 1.85 and the variance in each of the conditions is 4.0. The graph shows the power of the test as a function ofthe population correlation between the two scores for the 0.10, 0.05, and 0.01 significance levels. The power of an independent-groups t test (which assumes the correlation is 0) is shown by the x's.

Experiment with different combinations of the parameters. Is the correlation an important factor in power?

Illustrated Instructions

Video Demo
The demonstration starts by dragging each of the 5 points to different locations on the Y axis. Notice how these changes influence the total deviation and area. The video continues by repositioning the regression line by draggin either end as well as the middle. Finaly the regression line that minimizes the squared errors is found by clicking the "OK" button.

Video Demo